<meta charset="UTF-8">
<input type="button"  id="btn"  />
<script>
    setTimeout(close,10000);
    var i = 10;
    btn.value = "点击"+i+"秒关闭该网页";
    function f1(){
        i--;
        btn.value = "点击"+i+"秒关闭该网页";
    }
    setInterval(f1,1000);
</script>
